The present invention relates as indicated to an antisurveillance device which can prevent bugging of a telephone and relates more particularly to an enclosure for a telephone which completely surrounds the telephone in a sound-proof environment. Within the device, a signal generator emits noises that effectively interfere with those sounds which manage to penetrate the walls of the housing. The device is an obvious aid in improving security in any home, government office or business and eliminates the possibility that a telephone may be used to surreptitiously overhear private conversations.
Of all the methods presently employed in telephone surveillance, the most surreptitious of these is the "infinity bug". By the use of sophisticated electronic equipment, any telephone at short or long distance can be clandestinely converted into an open microphone. This is achieved even though the telephone is not in use and the handset is properly cradled. All sound and conversation that occurs in the vicinity of the telephone can therefore be heard and recorded. The present invention is a sound-proof enclosure in which the telephone is retained in complete isolation, thereby making such surveillance impossible. In addition, the device has an internal signal generator constantly emitting sounds in the confines of the enclosure. These generated signals cannot be heard outside the enclosure and are discontinued only when the enclosure is open for use of the telephone or when the signal generator power source is disconnected. An external telephone bell is provided to indicate incoming phone calls.
Enclosures for telephone devices have been shown generally in the prior art. However, they have not been of such a design as to prevent the bugging of the telephone, because the devices known previously have not been of such a design as to totally isolate the enclosed telephone from external sounds. For example, U.S. Pat. No. 925,775, is directed to a telephone box or casing which is weather-proof and constructed of sound absorbing material, but having an opening through which one may speak into the telephone transmitter. Such a device would clearly not be suitable for preventing the entry of all external sounds. Furthermore, no signal generating means is provided within the telephone box. U.S. Pat. No. 1,424,863, shows the use of a telephone box, the purpose of which is to prevent damage to a sub-station telephone from lightning. It consists of a lockable housing for holding the telephone equipment and has a key switch for disconnecting the equipment when not in use. The box has no sound insulating properties and would not prevent bugging by modern electronic equipment.